var people = {
    firstname: "ma",
    lastname: "hu",
    age: 23
}
var number = [1, 3, 4, 5, 6, 7]
number.push(10);
console.log(number)
let num = number.sort();
console.log(num)
let last = number[number.length - 1]
console.log(last)
number.forEach(function(i) {
    number[i] + 2;
})
console.log(number)
var a = Array.isArray(number);
console.log(a)
var b = number.join("$")
console.log(b)

// var a = typeof windows;
console.log(typeof {});
console.log(isNaN(NaN))